This invention relates to apparatus for aerating liquids, and in particular to portable machines for preparing aerated beverages. More especially, the invention concerns such machines intended for use in the home and adapted to be operated manually.
In aerating machines of the foregoing kind, a bottle containing the liquid to be aerated is loaded onto the machine and gas is introduced into the machine and passed through the liquid contained in the bottle. The bottle is subsequently removed, when the aerating has been completed.
The gas used for aerating is supplied from a cylinder fitted to the machine, which is replaced when it has become exhausted. A valve is provided to control the flow of gas from the cylinder, which, in the case of rechargeable cylinders, may form part of the cylinder, or in the case of disposable cylinders may form part of the machine. When the valve is operated, gas may pass into the machine and through the liquid, generating an internal pressure inside the machine and bottle, which is limited to a given maximum level by a pressure relief and safety valve. When the aerating process has been completed, the pressure inside the machine and bottle is reduced to atmospheric level by opening a valve.
When plastic bottles are used, undesired and often dangerous phenomena may occur. Thus, if the pressure relief and safety valves malfunction while the machine is being operated, gas pressure may continue to build up inside the bottle to the point where the bottle material yields and the bottle expands in a ductile way. The bottle expansion takes place on the outside diameter, this being the most highly stressed area. In prior art machines, this expansion may continue until the bottle surface engages the internal profile of the surrounding cavity and pressurization continues to take place until bottle or machine failure results. This often causes explosion of the bottle and injury to the user may result. Prior art machines are incapable of preventing or controlling such harmful phenomena.
Even if the valves operate perfectly and no malfunction occurs, a bottle may be defective or become defective because of abuse in use. Distortion of the body shoulder or base shape coupled with a change in material properties may then occur. This can result in failure of the bottle when subjected to stresses caused by internal pressurization. Prior art machines will permit distorted bottles to be loaded in the normal manner and pressurized.
It is a purpose of this invention to provide apparatus for preparing aerated beverages which provides complete safety even when plastic bottles are used. More specifically, it is a purpose of this invention to provide such an apparatus which will not permit a bottle to be pressurized if it is dimensionally defective and in particular if it does not have the correct profile and is, e.g., larger or smaller than it should be.
It is another purpose of this invention to provide such an apparatus which will prevent explosion of the bottle or failure of the apparatus itself if a bottle yields and expands during pressurization.
It is a further purpose of the invention to provide an apparatus of the kind described which will prevent undesired and/or unsafe discharge of gas.
It is a still further purpose of the invention to provide an apparatus of the kind described, the safety features of which are operative even while the user actuates the aerating controls.
Other purposes and advantages of the invention will become apparent as the description proceeds.